Micro-alloyed oxygen-free copper alloy and its use

ABSTRACT

An oxygen-free copper alloy comprising oxygen-free copper and, micro-alloyed therein, about 1-250 ppm tin (Sn) and/or about 1-150 ppm manganese (Mn). The invention also relates to the use of said copper alloy.

[0001] The present invention relates to a copper alloy according to the preamble of claim 1. The invention also relates to the use of said copper alloy, particularly in weldable applications.

[0002] Good weldability is an important property in copper, particularly in connection with the manufacturing of tubes and conducting wires for tubular cables. The material often used in the conducting wires of tubes and tubular cables, such as coaxial cables and the like, is thin copper strip, which in the manufacturing process is bent to be tubular, and the free edges of the strip are typically welded together. In many cases the obtained tube is further processed by drawing or by corrugating after welding. Said cables are used for instance in connection with cables designed for various telecommunication purposes or for example in underwater cables. In known arrangements where an excellent electroconductivity is needed, there is typically used so-called oxygen-free copper (for instance Cu-OF/ Cu-OFE). However, the need has arisen to further develop the good welding and working qualities of oxygen-free copper.

[0003] The object of the present invention is to realize a copper alloy with an excellent electroconductivity and with an excellent weldability and post-welding workability.

[0004] The invention is characterized by what is specified in the claims.

[0005] The alloy according to the invention has several remarkable advantages. When adding small amounts of alloy agents, particularly tin and/or manganese, into the oxygen-free copper, extremely good results have been achieved as regards weldability and workability. By micro-alloying small amounts of tin and/or manganese into oxygen-free copper, the properties of the molten material melted in connection with the joining process have been improved, particularly as regards viscosity and surface tension. Both of said properties have a significant effect in the weldability of the copper alloy. By means of the alloy according to the invention, there is achieved both a welding process that is easier to control, and a joint that is mechanically stronger. The achieved alloy is very well suited to be used in connection with products—for example tubes, profile tubes, corrugated tubes and tubular cable wires—that are manufactured of copper strips by welding, and in connection with the working of said products, for example drawing, bending, corrugating, profiling etc.

[0006] The invention is described in more detail below with reference the appended drawing, where the results of an example illustrating the invention are represented in graphical form.

EXAMPLE 1

[0007] TABLE 1 Copper alloys, their electroconductivity, weldability and post-welding workability. Cu + Ag Mn Sample (%) Sn (ppm) (ppm) O₂ (ppm) IACS (%) Cu—OF >99.95 <10 101.75 Cu—OF + Sn >99.95 25 <10 101.67 Cu—OF + Mn >99.95 8-9 <10 101.63

[0008] Material samples, bent into tubular form and illustrated in table 1, were welded. The employed materials were oxygen-free copper micro-alloyed with tin (CuOF+Sn) and oxygen-free copper micro-alloyed with manganese (Cu-OF+Mn), and the employed reference materials were oxygen-free copper (Cu-OF, applicant's quality type OF-OK). The micro-alloyed samples were the following:

[0009] Cu-OF+Sn alloying: 25 ppm Sn

[0010] Cu-OF+Mn alloying: 8-9 ppm Mn

[0011] The references used in the experiments were oxygen-free copper (Cu-OF). The thickness of the strip to be welded was 0.26 mm.

[0012] The welding experiments were performed by bending the material strip into tubular form and by welding the strip edges together with TIG welding. The employed equipment was a typical equipment used for welding tubes, where the material strip is first conducted, via bending rollers, into a welding position, where the opposite edges of the strip that is bent into tubular form are welded together. After the welding step, the welded tube is wound or conducted to a coil. The employed welding method was TIG welding, which is typically used In the welding of copper tubes. The employed protective gas was Argon. The welding rate was 20 m/min. The welding current fluctuated within the range of 100-250 A, and the welding voltage was roughly 9-12 V.

[0013] The welding experiments were successful. As regards the setting of welding values, with a quality that was micro-alloyed with tin it was easier to reach the correct setting values both for the shaping roller arrangement that bends the material strip to be welded, and for the welding values. The behavior of the melt of the Sn alloy could be controlled extremely well throughout a wide range of parameters. Also the Mn-alloyed material had better weldability than normal oxygen-free copper.

[0014] In the experiments that were carried out, it was found out that the weldability of oxygen-free copper micro-alloyed with tin (tin 25 ppm) was remarkably improved and was found excellent. Weldability was also improved by micro-alloying oxygen-free copper with small amounts of manganese (manganese 8-9 ppm). In the experiments, the weldability of oxygen-free copper micro-alloyed with manganese was estimated to be weaker than the weldability of oxygen-free copper micro-alloyed with tin. For a man skilled in the art, it is obvious that also other oxygen-free copper qualities (for instance Cu-OFE, Cu-OFXLP and C10910 (CDA code)) can be micro-alloyed in a similar way.

[0015] The welded tubes were subjected to an eddy current control. The evaluation was carried out by observing the results given by an eddy current meter. The evaluations are collected in table 2 and in FIG. 1. Part of the welded tubes were subjected to eddy current measurements. The evaluation was carried out by observing the results given by the eddy current meter. The obtained grade was affected by the height of the background noise caused by the weld, and possible peaks in the signal reduced the grade. In the eddy current analysis, a measurement carried out throughout a stretch of 30 m was applied. TABLE 2 Welding parameters and evaluation of the welds Grade Current Voltage Velocity Eddy Sample Alloy [A] [V] [m/min] Gas current 79 SN 156 9.4 20 AR 6 80 SN 146 9.3 20 AR 6 81 SN 136 9.5 20 AR 6 82 SN 126 9.6 20 AR 5.5 83 SN 116 9.6 20 AR 5 84 SN 105 9.7 20 AR 5 85 SN 166 9.5 20 AR 5 86 SN 176 9.5 20 AR 5 87 SN 196 9.5 20 AR 4.5 88 SN 210 9.5 20 AR 4.5 89 SN 220 9.5 20 AR 2 90 SN 156 10.2 20 AR 5 91 SN 176 10.2 20 AR 5 92 SN 166 10.1 20 AR 5 93 SN 196 10.1 20 AR 6 94 SN 210 10.2 20 AR 1 95 SN 200 11.3 20 AR 2 96 OF 200 10.1 20 AR 2 97 OF 200 10.1 20 AR 2 98 OF 176 10 20 AR 1 99 OF 176 8.9 20 AR 4 100 OF 166 8.9 20 AR 3 101 OF 166 9.3 20 AR 5 102 OF 176 9.5 20 AR 5 103 OF 176 10.4 20 AR 5 104 OF 176 11 20 AR 3 105 OF 196 11 20 AR 5 60 OF 196 11.1 20 AR 4 61 OF 210 11.2 20 AR 5 62 OF 220 11.3 20 AR 4 106 MN 166 10.1 20 AR 3 107 MN 176 10 20 AR 3 108 MN 186 10.1 20 AR 4 109 MN 196 10.1 20 AR 5

[0016] In the table, the alloy symbol SN means oxygen-free copper alloyed with tin (Cu-OF+Sn), the alloy symbol MN means oxygen-free copper alloyed with manganese (Cu-OF+Mn) and OF means ordinary oxygen-free copper (Cu-OF).

[0017] In FIG. 1, the oxygen-free copper alloyed with tin (Cu-OF+Sn) is marked with a square. The oxygen-free copper alloyed with manganese (Cu-OF+Mn) is marked with a circle. The oxygen-free copper (Cu-OF) used as reference material is marked with a triangle.

[0018] On the basis of FIG. 1 and table 2, it is found out that oxygen-free copper alloyed with tin (Cu-OF+Sn) was absolutely best in quality and made it possible to use the widest range of welding current. The welds obtained good grades throughout a wide range of current, i.e. 105-190 A. Likewise, oxygen-free copper alloyed with manganese (Cu-OF+Mn) also resulted in better-quality welds within a wider welding current range than ordinary oxygen-free copper (Cu-OF) used as reference material. On the basis of the deviation of results and the current range (current window) of the different materials, it can be maintained that the weldability of oxygen-free copper micro-alloyed with tin and/or manganese is clearly better. In particular, it was found out that among the tested materials, oxygen-free copper micro-alloyed with tin was best in terms of weldability.

[0019] The copper alloy according to the invention comprises oxygen-free copper (for example Cu-OF/Cu-OFE) and, micro-alloyed therein, about 1-250 ppm, typically 1-120 ppm, preferably 10-30 ppm, tin (Sn) and/or about 1-150 ppm, typically 1-70 ppm, preferably 5-20 ppm, manganese (Mn). The electroconductivity of the copper alloy is over 100% IACS, typically over 101% IACS, preferably over 101.5% IACS.

[0020] The invention also relates to the use of copper alloy:

[0021] As a conductor strip;

[0022] To the use of copper alloy as tubular wires in wire cables, such as a coaxial cables;

[0023] To the use of copper alloy in weldable conductor arrangements;

[0024] To the use of copper alloy in weldable and workable conductor arrangements;

[0025] To the use of copper alloy as tubular wire in underwater cables; and

[0026] To the use of copper alloy as corrugated tubes. 

1. An oxygen-free copper alloy, characterized in that said alloy comprises oxygen-free copper and, micro-alloyed therein, about 1-250 ppm tin (Sn) and/or about 1-150 ppm manganese (Mn) in order to improve the weldability of the alloy.
 2. A copper alloy according to claim 1, characterized in that said copper alloy comprises tin (Sn) 1-120 ppm, preferably 10-30 ppm.
 3. A copper alloy according to claim 1 or 2, characterized in that said copper alloy comprises manganese (Mn) 1-70 ppm, preferably 5-20 ppm.
 4. A copper alloy according to any of the claims 1-3, characterized in that the electroconductivity of said alloy is over 100% IACS.
 5. A copper alloy according to any of the claims 1-4, characterized in that the electroconductivity of said alloy is over 101% IACS.
 6. The use of a copper alloy according to any of the claims 1-6 as conductor strip.
 7. The use of a copper alloy according to any of the claims 1-6 as tubular wire in conductor cables, such as coaxial cables.
 8. The use of a copper alloy according to any of the claims 1-6 in weldable conductor arrangements.
 9. The use of a copper alloy according to any of the claims 1-6 in weldable and workable conductor arrangements.
 10. The use of a copper alloy according to any of the claims 1-6 as tubular wire in underwater cables.
 11. The use of a copper alloy according to any of the claims 1-6 in corrugated tubes. 